The (sum) value is a summary of all rail powers and if you look at the maximum values, you'll notice that some rails report invalid data sometimes: +3.3V, +5V and +12V report 12.2V maximum, which is not valid. So all particular max power values including (sum) are invalid too.
Such invalid values are most probably caused by running the Corsair software together with HWiNFO, which results in conflicts during access. There are a few threads about this on this forum.